The present invention relates to a method and an apparatus of piling veneer sheets, and more particularly, to a method and an apparatus of piling veneer sheets so that one edge of the sheets is vertically aligned with each other, to simplify the succeeding plywood manufacture process.
The plywood manufacture process includes a process to pile a plurality of veneer sheets which are cut into predetermined dimensions. To this end, a plurality of veneer sheets should be transferred to a piling position in layers in such a condition that the edges of the layers are vertically aligned with each other.
Conventionally, step-like arranged two conveyers are controlled by output signals of photoelectric cells to detect each veneer sheet on each conveyer. When the photoelectric cell detects a veneer sheet, the conveyer is stopped. After both conveyers are stopped, both conveyers are started again so that the veneer sheet on the upper conveyer is passed beyond the front edge of the conveyer and is overlaid on the veneer sheet of the lower conveyer. However, the stops and starts of the conveyers are difficult to synchronize for the veneer sheets overlaid condition enabling the front edges of the veneer sheets to align vertically. Sometimes, the stagger amount between the front edges is some tens of millimeters, thus yield rate and quantity of plywood are unsatisfactory. To manufacture plywoods of determined dimension, the veneer sheets must be wide enough to include the stagger. Further, the process of piling up desired veneer sheets is performed by two stages, so that the apparatus is complex and is difficult to maintain. Further, total piling time is long, and productivity is low.
Another conventional process to pile veneer sheets utilizes a conveyer having two parallel conveyer belts to support both lateral opposite edge portions of a veneer sheet. When the front edge of the veneer sheet reaches a predetermined position, the conveyer is stopped and the conveyer belts are opened laterally to drop the veneer sheet downwards. Dropped sheets are piled under the conveyer. Another proposed apparatus provides pressing means which contacts the upper surface of the veneer sheet before the belts are opened, and presses the veneer sheet downwards as the belts are opened laterally. However, such conventional apparatus can not prevent the veneer sheet from floating horizontally or radially while dropping, so that the front edges of the piled sheets do not correctly align vertically.
In actual process, the edges of the sheets are aligned manually, so that many workers must be employed, and low productivity is the result.